#define  _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<math.h>
int main()
{
	int n,a=1;
	float sum = 0,b=0;
	scanf("%d", &n);
	for (a = 1; a <= n; a++)
	{
		b = pow(-1, a + 1);
		sum=sum+ (1.0 / a * b);//1  1; 2 1-1/2
	}
	printf("%f",sum );
	return 0;
}